Links to Picasa Web Albums and photos get emailed around all the time. Now, if you use Gmail and turn on Picasa previews from the Gmail Labs tab under Settings, you won't even have to leave your inbox to preview your photos -- instead, they'll show up right inside your messages, like this:

Recipients will see image previews whether you use the "Share" button in Picasa Web Albums, or simply include a Picasa Web Albums link in your email.